US Chinese food vs Real Chinese food

I've hear people that were born in China and come to the US to try our Chinese restaurants say that they're very different compared to the food that's actually served in China. 

Can someone explain the differences in our perception of Chinese food and what's actually over there?

>>20
well the dishes you get at a chinese restaurant are called 'song' which basically means accompany. the dishes are there to go with the rice.